Treatment of hydrocarbons



Patented Aug. 16, 1938 UNITED STATES PATENT orrlcs TREATMENT OF HYDBOCABBCNS Jacque C. Morrell, Chicago, 111., aasignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware No Drawing. Application February 27, 1936,

Serial No. 66,065

dustry has been continually confronted with the problem of increasing both the quantity and the quality oi. its motor fuel products, particularly from an antiknock standpoint, and has metthe late and residual fractions of petroleum produced in the primary distilling processes to produce additional yields of light oil. Fortunately, since the reactions of cracking involve principally dehydrogenation and cyclization reactions the antiknock properties of cracked motor fuel fractions are unusually good. and the gasolines thus produced need only" limited treatment to render them suificiently' stable for use as automotive engine fuel. Thus, very limited treatments remove the more reactive diolefins and. to some extent, the corrosive or malodorous sulfur. compounds, or they may be sufficiently stabilized by the use of selective inhibitors. However, as the antiknock value of cracked gasolines is raised by more and more intensive cracking, the yields necessarily decrease on account of the loss of hydrogen, and a point is reached where the increase in antiknock value is more than counterbalanced by the decrease 'in yield so that further cracking is not economical.

In all cracking processes for the production of gasoline there is an incidental concurrent production of fixed gases which contain high per- 45 fins and free hydrogen. For purposes of'reference the following table shows the hydrocarbon, compounds which have been definitely identified in cracked 'gas mixtures:

Methane, Ethane, Ethylene, Acetylene, Propane, Propylene,

The ratio of unsaturated hydrocarbons to' paraflins depends, to a considerable extent, upon the conditions of cracking, the relatively high temperature and low pressure processes currently Butanes, Butylenes, Pentanes, Amyl e Butadienes.

Within the past few years the petroleum. in-

problem largely bycracking the heavier distilcentages of olefinic constituents as well as parafdesignated as vapor phase? processes favoring the production of olefins, and particularly ethylene, as conditions of great severity are employed. Since the total production of gases in cracking operations may run from .5 to as high as 20 per cent by weight of thestock cracked, it is obviously important to make some utilization-of 'these gases and, if possible, reconvert them'into gasoline. The primary point of attack is obviously to condense or polymerize the olefins and this has been attempted by various thermal'and 'catalyticprocesses which are more or less commercial at the present time. It is with an improvement in the art of catalytically polymerizing the oleflns in cracked gas mixtures that the present invention is especially concerned,

In one specific embodiment, the present invention comprises subjecting hydrocarbon gas mixtures containing isobutylene to the actionof catalysts comprising essentially a mono-,metallic phosphate, particularly ortho-phosphates, which are selective in polymerizing the isobutylene to form 2,2,4-trimethyl pentene and perhaps, to

some extent, isomers thereof by mixed polymerization, which is hydrogenatable to form the cor-v responding octane.

.Experiments on olefin-containing gas mix- Y 'tures, on olefin mixtures, and on individual olefins, have indicated that, of the normally gase ous olefins, isobutylene is most susceptible to polymerizing influences and that ethylene is the least susceptible. In catalytic processes, therefore there is a tendency for the isobutylene to be removed under relatively mild conditions of temperature, pressure and catalytic influence, though there is usually some concurrent mixed polymerization in which the iso and normalbutenes' combine to form octenes. This reaction may occur, tosome extent, in the present invention. Since the various isomers thus pro' duced boil within rather close ranges of temperature, there may be considerable difllculty in separating them when only the dimer of isobutylene is desired in the product. 'The phenomenon of mixedpolymerization, which produces compounds which may be consideredto contaminate this puredimer, is observed with various catalysts and particularly-with phosphoric acid catalysts, either liquid or the so-called solid" variety, which consists of a relatively inert siliceous carrier impregnated with an acid of phosphorus, usually the. pyro acid or one.

closely approaching this in composition in most stantially only the isobutylene is affected and the desired dimer. which may be readily hydrogenated to produce 2,2,4-trimethyl pentane, is produced in a state of comparative purity.

The preferred catalysts: comprise the mono metallic-ortho phosphates o! the alkali and the alkaline earth metals, though some of the so.- called heavy metal compounds may be successfully employed. These compounds have a generally weaker polymerizing action than catalysts which comprise some acid phosphorus as their active constituent, on account of the partial replacement of the acid hydregen by bases. Below are listed a few of the compounds which may be employed:

Ca(H2PO4) Mk0--. Mono-calcium phosphate.

Mg(I-l2PO4)2 Mono-magnesium phosphate. B8.(H2PO4)2 Mono-barium phosphate. SI'(H2PO4)2 Mono-strontium phosphate. NaHzP04.H2O Mono-sodium phosphate. KH2PO4 Mono-potassium phosphate.

The monoalkali metal phosphates are soluble in water and normally best utilized after being mixed within some definite mesh range, usually form 4 In polymerizing insobutylene by the use of the preferred catalysts, they are most conveniently employed as filler in vertical cylindrical treating towers, the gas mixture to be treated being preheated to a suitable temperature and pwsed downwardly through the bed of catalyst at an.

lene in the gas mixture. In the case of the calcium compound, which is easily procurable and quite eflective, temperatures from 300 to 500 F.

' may be employed. The process is particularly suitable for the treatment of the overhead products from stabilizers operating upon primary cracked distillates, which comprise principally hydrocarbons of three and four carbon atoms, including propane, propylene, butanes and butylenes, and in which isobutylene may occur from approximately 5 to 15% concentration depending upon the character of the cracked distillate un dergoing stabilization although gases direct from a cracking process may be treated. Thesemixtures may be pumped as liquids and vaporized during passage through heating elements in which they are raised to the temperature found most suitable for the selective removal of isobutylene, using a catalyst selected from the present group. The liquid dimer is readily separated irom the uhaflected residual gases and the latter may then be subjected to more severe conditions of temperature, pressure and catalytic influence, such as the plated within the scope of the process) in order to produce further quantities of liquid polymers which may have a sufllciently highoctane number to render them well suited to blending with gasolines inferior in antiknock value.

The dimer of isobutylene is readily hydrogenated under moderate conditions, such as a temperature of about 500 F. and a hydrogen pressure of ,1000 lbs. per square inch, while using such catalysts as nickel oxide or the sulfides of the commoner elements in the sixth group of the periodic table, including chromium, molybdenum or tungsten. This step 01' the process may follow continuously from the other.

The following example is introduced to show the character of the results obtainable by the use of the present process, although it is not intended to limit the scope of the invention in exact correspondence with the date presented.

A mixture of hydrocarbons constituting the overhead from a cracked gasoline stabilizer and comprising 8% by volume (on a gas basis) of isobutylene was passed downwardly through a bed of granular mono-calcium-ortho-phosphate at a temperature of 350 F. and a pressure of 500 lbs. per square inch. Under these conditions the dimer of isobutylene was produced in a condition or 95% purity, the additional 5% being a mixture of dimers which were removable by a fairly careful-fractionation, the, normal butylenes and propylene being substantially unaffected by the treatment. Good results were also produced when cracked gases direct were treated with the phosphate catalyst and combination treatment e. g. following the present process by the use of a stronger polymerizing agent to polymerize the residual oiefins also gave good results.

The character or the present invention and the definitely practical value thereof will be evident from the ioregolngspecification and single instance of results obtained, though neither section is intended ,to be unduly-limiting.

I claim as my invention:

1. A process for producing iso-octene from a hydrocarbon gas mixture containing isobutylene and other polymerizable gaseous olefins, which comprises subjecting the mixture at a temperature of from 250 to 550" F. to the action of a mono-metallic-ortho-phosphate to selectively polymerize isobutylene from the mixture and separating the resultant polymer from the unpolymerlzed gases.

' 2. A process for producing iso-octene from a hydrocarbon gas mixture containing isobutylene andother polymerizable gaseous oleflns, which comprises subjecting the mixture at a temperature'of from 250 to 550 F. to the action of a mono-metallic-ortho-phosphate .or an alkalinous metal to selectively polymerize isobutylene from the mixture, and separating the resultant polymer from the unpolymerized gases.

3. A process for producing iso-octene from'a hydrocarbon gas mixture containing isobutylene and other polymerizable gaseous oleflns. which comprises subjecting the mixture at a temperature of from 250 to 550 F. to the action or a mono-calciuni-ortho-phosphate to selectively polymerize isobutylene from the mixture, and separating the resultant polymer from the unpolymerized gases.

JACQUE C. MORREIL. 

